First off, sorry you're joining this board, but you've found an awesome support group of women who know exactly how you feel.
As for your questions, I started my m/c at 4 weeks, 4 days, so I can relate really well. I actually had cramps most of the night before and while sleeping. I spotted that morning, but I didn't start bleeding until the afternoon, and it was heavy. I had very bad cramping (the worst menstrual cramps ever) that afternoon for about three hours. After I got through those few hours, I just had minor crampiness most of the next day. I bled very heavily the second day as well. Unlike a normal period for me, there was a lot more clotting. By the third and fourth days, I was just spotting. So it lasted pretty much the length of a normal period for me, but it was a lot heavier. I had a follow-up exam exactly one week later, and the doctor noted that I did still have some blood mixed in with my CM, but I hadn't noticed it by that point.
That happened just last cycle. I continued to chart the whole time. So you can click on my ticker below to see the progression of my pregnancy cycle and this subsequent cycle. Fortunately, my hCG dropped back to 0 quickly. So DH and I decided to go ahead and try again this cycle. I'm gearing up to O pretty soon (I think).
My doctor told me that the next couple of cycles could be irregular. The biggest difference I have noted is my temps. They were slow to come down after the m/c, and they are about a degree higher than they were at this point last cycle. I also, unfortunately, got a yeast infection, which the doctor figured was a result of the crazy hormone fluctuations.
Sorry if that was TMI, but I just thought since our circumstances were so similar that you might benefit from hearing it all. I'd be happy to answer any specific questions if you have them.
And, once again, I'm so sorry you're going through this.